Non-return valve

ABSTRACT

What is disclosed is a non-return valve comprising a sealing piston which is biased against a valve seat in the basic position inside a valve housing, and which is manufactured by a plastics injection molding technique.

The invention relates to a non-return valve in accordance with thepreamble of claim 1.

Non-return valves have the function of blocking a pressure medium flowin one direction and admit a volume flow in the opposite direction.

A like non-return valve is disclosed in the applicant's data sheets RD20 395/10.95. There, a metallic sealing piston adapted to allow a flowtherethrough is received in a valve housing and is in a basic positionbiased against a valve seat, so that a pressure medium connectionbetween two working ports is blocked in the direction of flowtherethrough.

It is a drawback of the known solution that the complexity inmanufacturing the metallic sealing piston is very high.

Moreover it is a drawback in the known solution that it has a strongtendency to sealing defects.

Moreover it is disadvantageous that the metallic sealing piston isheavy, so that the non-return valve exhibits relatively sluggishresponse characteristic.

It is an object of the present invention to furnish a non-return valvethat eliminates the above mentioned drawbacks and may be manufactured ata low cost.

This object is attained through a non-return valve having the featuresin accordance with claim 1.

In accordance with the invention, a sealing piston of a non-return valveis manufactured by a plastics injection molding technique. It is anadvantage of this solution that the sealing piston in accordance withthe invention may be manufactured with little complexity and in acost-efficient manner. Moreover the plastics surface of the sealingpiston of the invention is relatively soft, so that a good tightness maybe ensured. Moreover the sealing piston of the invention ischaracterized by a low weight, so that the non-return valve exhibitssensitive response characteristics.

A preferred plastics material is poly-ether-ether-ketone (PEEK) in whichcarbon fiber, preferably in a proportion of 30%, may be integrated so asto enhance stiffness of the sealing piston.

The sealing piston is guided on the drain side, with recesses beingprovided in its outer periphery so as to reduce hysteresis. Between therecesses, axial webs are preferably left, the guide surfaces of whichare wetted by the pressure medium in the spring chamber, to thus permitoptimum guiding of the sealing piston. In one embodiment, six recesseswith six intermediate webs are provided.

In the opened position, pressure medium may flow into the spring chambervia a star configuration of bores. In order to improve guiding of thesealing piston, and for reinforcement, guide projections may be formedbetween the bores of the star configuration of bores. The guideprojections are preferably triangular and taper in an upstream directionagainst the direction of pressure build-up, with their axial lengthpreferably corresponding to the inner diameter of the bores. The innerdiameter and number of the bores are selected with a view to arespective optimum cross-section of flow. Preferably four bores areprovided.

In order to avoid a generation of turbulences of the pressure mediumflow in the opened position, the sealing piston may have a front-sideflow-receiving cone on the supply side. The flow-receiving cone may havea rounded or hemispherical head.

A spring for biasing the sealing piston is in one preferred embodimentsupported on a spring cup, equally made of plastics, in the basicposition. Preferably the spring cup has on its outer periphery at leastone radial sealing lip, so that the spring chamber is closed sealingly.Moreover at least one sealing lip may be formed on the front side on thespring cup. Particularly good sealing properties are obtained if theradial sealing lips are inclined opposite to the direction of pressurebuild-up, and the front-side sealing lips are inclined in the directionof pressure build-up.

Other advantageous embodiments are the subject matter of furthersubclaims.

In the following a detailed explanation of a preferred embodiment of theinvention will be given by referring to schematic representations,wherein

FIG. 1 is a lateral view of an embodiment of a non-return valve inaccordance with the invention, and

FIG. 2 is a longitudinal sectional view of the non-return valve of FIG.1.

FIGS. 1 and 2 show a lateral view of a preferred embodiment of adirectly controlled non-return valve 2 in accordance with the invention,and an enlarged longitudinal sectional view including a sealing piston 4adapted for a flow therethrough, which is received in a longitudinalbore 6 of a valve housing 8. The longitudinal bore 6 extends between acoaxial connection bore 10 for connection of a supply-side working portA and a coaxial connection bore 12 of a coupling plate 14 of adrain-side working port which closes the longitudinal bore 6. In itsbasic position, the sealing piston 4 is biased by a spring 16 against avalve seat 18. The spring 16 is arranged in a spring chamber 20 andsupported on a spring cup 22 in the longitudinal bore 6. It plunges intoa reception bore 24 of the sealing piston 4 (FIG. 2) and attacks on anannular bottom surface 26 of the reception bore 24.

The sealing piston 4 is in accordance with the invention manufactured byan injection molding technique. It consists of plastics and may bereinforced with carbon fiber. Preferably the selected plastics ispoly-ether-ether-ketone (PEEK) and reinforced with 30% of carbon fiber.The sealing piston 4 is executed in the form of a hollow piston, withthe reception bore 24 being radially tapered in the direction of aflow-receiving side 68 of the sealing piston 4. Bores 54 of a starconfiguration of bores 52 merge into this taper 70. In the openedposition, pressure medium may thus enter into the sealing piston 4 viathe valve seat 18 through the bores 54 and flow into the spring chamber20 on the rear chamber side. In order to improve the flowcharacteristics, the bores 54 obliquely merge into the taper 70 in thedirection of pressure build-up. The shape and number of bores 54 isselected such that the cross-section of flow of the bores 54 isoptimized. Preferably four bores 54 are provided.

In order to homogenize the pressure medium flow, a flow-receiving cone56 is formed on the flow-receiving side 68 of the sealing piston 4. Theflow-receiving cone 56 continues into a hemispherical head 64, with theperipheral surface 72 of the head 64 being inclined more steeply thanthe one of the flow-receiving cone 56.

The sealing piston 4 is radially guided in the longitudinal bore 6 onthe drain side, with a multiplicity of radial recesses 48 being providedin its outer periphery 46 so as to avoid one-sided guidance of thesealing piston 4 in the longitudinal bore 6 and thus reduce hysteresis,so that the sealing piston 6 is guided through the intermediary ofsingle axial webs 50 separating the recesses 48 from each other, and anarrow annular collar 62 at the bottom 76 of the recesses 48.

The pocket-type recesses 48 are open towards the spring chamber 20 andextend in the manner of fingers in a direction towards theflow-receiving cone 56. The number of recesses 48 is optimized withregard to the width of the peripheral guide surfaces 66 of the webs 50.Preferably six recesses 48 with six webs 50 are provided.

The annular collar 62 continues in an upstream direction towards theflow-receiving cone 56 into axial triangular guide projections 58. Theguide projections 58 extend between the bores 54 and taper in adirection towards the flow-receiving cone 56. The axial length of theguide projections 58 is preferentially selected such that it aboutcorresponds to the inner diameter of the bores 54. In the range of theguide projections 56, the sealing piston 4 has the same outer diameteras in the range of the annular collar 62 and in the range of the webs50, so that the sealing piston 4 is equally guided in the longitudinalbore 6 through the intermediary of the guide projections 58 and thus theaxial length of guidance is correspondingly extended by the axial extentof the guide projections 58. As a result of arranging the guideprojections 58 between the bores 54, this range of the sealing piston 4that is structurally weakened by the bores 54 is additionallyreinforced.

The spring cup 22 is manufactured of a plastics material that ispreferentially softer than the plastics of the sealing piston 4. It isinserted in a radial undercut 28 of the longitudinal bore 8 and axiallyimmobilized in its position through contact with the coupling plate 14.The axial length of the undercut 28 is selected such that oppositesurfaces 30, 32 of the coupling plate 14 and of the valve housing 8 arespaced apart in the assembled condition, and the coupling plate 14 isonly taken into contact with the spring cup 22, so that the latter ispushed against a shoulder 74 of the undercut 28. In order to allowdraining of the pressure medium from the spring chamber 20, a throughbore 34 coaxial with the longitudinal bore 6 of the valve housing 8 andwith the connection bore 12 of the coupling plate 14 is formed in thespring cup 22.

At the outer periphery 42 of the spring cup 22, radial sealing lips 36for sealing the spring chamber 20 against the coupling plate 14 areprovided. The sealing lips 36 extend in parallel and are formed byannular grooves 38. The sealing lips 36 extend obliquely to thelongitudinal axis of the longitudinal bore 6, and are inclined againstthe direction of pressure build-up in a direction towards the valve seat18 when viewed from groove bottoms 60 of the annular grooves 38. Thisoblique orientation in combination with the soft plastics has theadvantage that the sealing lips 36 are automatically straightened up orinclined as a result of the pressure medium and thus are pushed againstthe inner periphery 40 of the undercut 32 of the longitudinal bore 6.For sealing the drain-side connection bore 12 of the coupling plate 14,there is provided on the front side at least one sealing lip 44 inclinedobliquely relative to the longitudinal bore 6, however in contrast withthe radial sealing lips 36 inclined in the direction of pressurebuild-up, so that they may be inclined or straightened up by thepressure of the draining pressure medium.

By manufacturing the sealing piston 4 by a plastics injection moldingtechnique, complexity of manufacture is thus substantially reduced, andthe sealing piston 4 may accordingly be manufactured at low cost andrapidly.

Moreover good sealing may be obtained through the fact that owing to therelatively soft plastics surface of the sealing piston 4, pollutionsfrom the pressure medium that are deposited, e.g., on the valve seat 18may be impressed into the sealing piston 4.

Thanks to the use of plastics in accordance with the invention, thesealing piston 4 may be executed substantially more easily than knownmetallic sealing pistons, so that the non-return valve 4 of theinvention exhibits improved response characteristics. These responsecharacteristics are additionally improved by the recesses 48 in theouter periphery 46 of the sealing piston 4, wherein the axial guidinglength of the webs 50 of the sealing piston 4 is prolonged by the guideprojections 58. Moreover the response characteristics of the non-returnvalve 2 of the invention are improved by the flow-receiving cone 56, forthe pressure medium may have an optimum flow onto the sealing piston 4and may in the opened position flow off better across the valve seat 18.

It is obvious that even though the above described embodiment shows anon-return valve having two axial working ports, the sealing piston 4 ofthe invention may also be employed in non-return valves having one axialand one radial working port.

What is disclosed is a non-return valve comprising a sealing pistonwhich is biased against a valve seat in the basic position inside avalve housing, and which is manufactured by a plastics injection moldingtechnique.

LIST OF REFERENCE NUMERALS

-   -   2 non-return valve    -   4 sealing piston    -   6 longitudinal bore    -   8 valve housing    -   10 connection bore    -   12 connection bore    -   14 coupling plate    -   16 spring    -   18 valve seat    -   20 spring chamber    -   22 spring cup    -   24 reception bore    -   26 bottom surface    -   28 undercut    -   30 surface    -   32 surface    -   34 through bore    -   36 sealing lip    -   38 annular grooves    -   40 inner periphery    -   42 outer periphery    -   44 sealing lip    -   46 outer periphery    -   48 recesses    -   50 web    -   52 star configuration of bores    -   54 bores    -   56 flow-receiving cone    -   58 guide projection    -   60 groove bottom    -   62 annular collar    -   64 head    -   66 guide surface    -   68 flow-receiving side    -   70 taper    -   72 peripheral surface    -   74 shoulder    -   76 bottom

1. A non-return valve comprising a hollow sealing piston received in avalve housing and biased against a valve seat by means of a spring in abasic position, so that in the basic position a pressure mediumconnection between two working ports in the direction of flowtherethrough is closed, characterized in that the sealing piston ismanufactured by a plastics injection molding technique.
 2. Thenon-return valve in accordance with claim 1, characterized in that thesealing piston is manufactured of the plastics material PEEK.
 3. Thenon-return valve in accordance with claim 1, characterized in that thesealing piston is reinforced by 30% of carbon fiber.
 4. The non-returnvalve in accordance with claim 1, characterized in that the sealingpiston includes a multiplicity of recesses on the outer periphery, sothat the sealing piston is guided in the longitudinal bore by axial websdelimiting the recesses from each other.
 5. The non-return valve inaccordance with claim 1, characterized in that the sealing pistonincludes a star configuration of bores, through the bores of whichpressure medium may flow into a spring chamber in the opened position.6. The non-return valve in accordance with claim 4, characterized inthat six recesses and four bores are provided.
 7. The non-return valvein accordance with claim 5, characterized in that guide projections areformed between the bores.
 8. The non-return valve in accordance withclaim 7, characterized in that the guide projections have a triangularshape and taper in the flow-receiving direction.
 9. The non-return valvein accordance with claim 7, characterized in that the guide projectionseach have an axial length approximately corresponding to the innerdiameters of the bores.
 10. The non-return valve in accordance withclaim 1, characterized in that the sealing piston comprises aflow-receiving cone.
 11. The non-return valve in accordance with claim10, characterized in that the flow-receiving cone has a rounded head.12. The non-return valve in accordance with claim 1, characterized inthat the spring is supported in the valve housing by a spring cup madeof plastics.
 13. The non-return valve in accordance with claim 12,characterized in that the spring cup has at its outer periphery and/oron its front side at least one sealing lip.
 14. The non-return valve inaccordance with claim 13, characterized in that the radial sealing lipsare inclined against the direction of pressure build-up, and thefront-side sealing lips are inclined in the direction of pressurebuild-up.